Methods, systems, and computer readable media for providing for reliable service based interface (SBI) message transport using zero event notification messages

ABSTRACT

A method for providing for reliable service based interface (SBI) message transport using zero event notifications includes, at a consumer NF, sending an SBI message to a producer NF indicating an intent to use zero event notification messaging. The method further includes, at the producer NF, receiving the SBI message indicating the intent to use zero event notification messaging, and, transmitting a zero event notification request message to the consumer NF using a callback URI from the SBI message to confirm the callback URI and connectivity from the producer NF to the consumer NF. The method further includes, at the consumer NF, receiving the zero event notification request message and, in response, sending a zero event notification response message to the producer NF. The method further includes, at the producer NF, receiving the zero event notification response message, and, in response, continuing SBI subscription messaging with the consumer NF.

TECHNICAL FIELD

The subject matter described herein relates to providing for reliablemessage transport in communications networks. More particularly, thesubject matter described herein relates to methods, systems, andcomputer readable media for reliable SBI message transport using zeroevent notification messages.

BACKGROUND

In 5G telecommunications networks, a network function that providesservice is referred to as a producer network function (NF) or NF serviceproducer. A network function that consumes services is referred to as aconsumer NF or NF service consumer. A network function can be a producerNF, a consumer NF, or both, depending on whether the network function isconsuming, producing, or consuming and producing services. The terms“producer NF” and “NF service producer” are used interchangeably herein.Similarly, the terms “consumer NF” and “NF service consumer” are usedinterchangeably herein.

A given producer NF may have many service endpoints, where a serviceendpoint is the point of contact for one or more NF instances hosted bythe producer NF. The service endpoint is identified by a combination ofInternet protocol (IP) address and port number or a fully qualifieddomain name that resolves to an IP address and port number on a networknode that hosts a producer NF. An NF instance is an instance of aproducer NF that provides a service. A given producer NF may includemore than one NF instance. It should also be noted that multiple NFinstances can share the same service endpoint.

Producer NFs register with a network function repository function (NRF).The NRF maintains service profiles of available NF instances identifyingthe services supported by each NF instance. The terms “service profiles”and “NF profiles” are used interchangeably herein. Consumer NFs cansubscribe to receive information about producer NF instances that haveregistered with the NRF.

In addition to consumer NFs, another type of network node that cansubscribe to receive information about NF service instances is a servicecommunication proxy (SCP). The SCP subscribes with the NRF and obtainsreachability and service profile information regarding producer NFservice instances. Consumer NFs connect to the SCP, and the SCP loadbalances traffic among producer NF service instances that provide therequired services or directly routes the traffic to the destinationproducer NF instances.

In addition to the SCP, another example of an intermediate proxy nodethat routes traffic between producer and consumer NFs is the securityedge protection proxy (SEPP). The SEPP is the network node used toprotect control plane traffic that is exchanged between different 5Gpublic land mobile networks (PLMNs). As such, the SEPP performs messagefiltering, policing and topology hiding for all application programminginterface (API) messages that are transmitted between PLMNs.

One problem in 5G communications networks is that subscription relatedmessaging that takes place on the SBI interface can be unreliable. TheSBI interface is an HTTP interface used to communicate messages between5G NFs. One type of communications that occurs over the SBI interface issubscribe/notify communications. In a typical subscribe/notifycommunications procedure, a consumer NF requests creation of asubscription with the producer NF. If the producer NF accepts thesubscription, the producer NF responds to the consumer NF indicatingthat the subscription has been created. When the condition that triggersa notification associated with the subscription occurs, the producer NFtransmits a notification message to the consumer NF over the SBIinterface.

The notification message transmitted over the SBI interface includes acallback uniform resource identifier (URI) that is supposed to identifythe sending consumer NF. If the callback URI provided in thesubscription request message is incorrect or if there is a transportfailure between the consumer NF and the producer NF, the producer NFwill be unable to transmit notification messages successfully to theconsumer NF. If the notification is not successful, excessive delay inprocessing may result because the consumer NF is required to discoverthe failure, recreate the subscription with the producer NF, andsubsequently receive the notifications.

In light of these and other difficulties, there exists a need formethods, systems, and computer readable media for providing improvedreliability for subscription-related messages transmitted over the SBIinterface.

SUMMARY

A method for providing for reliable service based interface (SBI)message transport using zero event notifications includes, at a consumerNF, sending an SBI message to a producer NF indicating an intent to usezero event notification messaging. The method further includes, at theproducer NF, receiving the SBI message indicating the intent to use zeroevent notification messaging, and, transmitting a zero eventnotification request message to the consumer NF using a callback uniformresource identifier (URI) from the SBI message to confirm the callbackURI and connectivity from the producer NF to the consumer NF. The methodfurther includes, at the consumer NF, receiving the zero eventnotification request message and, in response, sending a zero eventnotification response message to the producer NF. The method furtherincludes, at the producer NF, receiving the zero event notificationresponse message, and, in response, continuing SBI subscriptionmessaging with the consumer NF.

According to another aspect of the subject matter described herein,sending the SBI message indicating an intent to use zero eventnotification messaging includes transmitting a hypertext transferprotocol (HTTP) message to the producer NF and including a parameter ina header of the HTTP message that indicates the intent to use zero eventnotification messaging and a timing as to when to use the zero eventnotification messaging.

According to another aspect of the subject matter described herein, theHTTP header indicates that the zero event notification messaging will beduring or after subscription creation.

According to another aspect of the subject matter described herein,transmitting the zero event notification request message includestransmitting the zero event notification request message as a part ofcreation of a subscription.

According to another aspect of the subject matter described herein,transmitting the zero event notification request message as part ofcreation of a subscription includes transmitting the zero eventnotification request message after receiving a subscription request fromthe consumer NF and wherein continuing the SBI subscription messagingwith the consumer NF includes transmitting a subscription response tothe consumer NF indicating successful creation of a subscription.

According to another aspect of the subject matter described herein,transmitting the zero event notification request message includestransmitting the zero event notification request message after creationof a subscription.

According to another aspect of the subject matter described herein,transmitting the zero event notification request message after creationof a subscription includes transmitting the zero event notificationrequest message after transmitting a subscription response message tothe consumer NF indicating successful creation of the subscription.

According to another aspect of the subject matter described herein,transmitting the zero event notification request message includestransmitting the zero event notification request message as part ofupdating a subscription.

According to another aspect of the subject matter described herein,transmitting the zero event notification request message includestransmitting the zero event notification request message after updatinga subscription.

According to another aspect of the subject matter described herein, thezero event notification request message comprises a dummy eventnotification message that does not correspond to a subscription event.

According to another aspect of the subject matter described herein, asystem for providing for reliable service based interface (SBI) messagetransport using zero event notifications is provided. The systemincludes a consumer NF including at least one processor and a memory forsending an SBI message indicating an intent to use zero eventnotification messaging. The system further includes a producer NFincluding at least one processor and a memory for receiving the SBImessage indicating the intent to use zero event notification messaging,and, in response, for transmitting a zero event notification requestmessage to the consumer NF using a callback uniform resource identifier(URI) from the SBI message to confirm the callback URI and connectivityfrom the producer NF to the consumer NF. The consumer NF is configuredto receive the zero event notification request message and, in response,send a zero event notification response message to the producer NF. Theproducer NF is configured to receive the zero event notificationresponse message, and, in response, continue with SBI subscriptionmessaging with the consumer NF.

According to another aspect of the subject matter described herein, theconsumer NF is configured to send the SBI message indicating an intentto use zero event notification messaging by transmitting a hypertexttransfer protocol (HTTP) message to the producer NF and including aparameter in a header of the HTTP message that indicates the intent touse zero event notification messaging and a timing as to when to use thezero event notification messaging.

According to another aspect of the subject matter described herein, theHTTP header indicates that the zero event notification messaging will beduring or after subscription creation.

According to another aspect of the subject matter described herein, theproducer NF is configured to transmit the zero event notificationrequest message as a part of creation of a subscription.

According to another aspect of the subject matter described herein, theproducer NF is configured to transmit the zero event notificationrequest message after receiving a subscription request from the consumerNF and to continue the SBI subscription messaging with the consumer NFby transmitting a subscription response to the consumer NF indicatingsuccessful creation of a subscription.

According to another aspect of the subject matter described herein, theproducer NF is configured to transmit the zero event notificationrequest message after transmitting a subscription response message tothe consumer NF indicating successful creation of the subscription.

According to another aspect of the subject matter described herein, theproducer NF is configured to transmit the zero event notificationrequest message as part of updating a subscription.

According to another aspect of the subject matter described herein, theproducer NF is configured to transmit the zero event notificationrequest message after updating a subscription.

According to another aspect of the subject matter described herein, anon-transitory computer readable medium having stored thereon executableinstructions that when executed by a processor of a computer control thecomputer to perform steps comprising is provided. The steps include, ata consumer network function (NF), sending a service based interface(SBI) message to a producer NF indicating an intent to use zero eventnotification messaging. The steps further include, at the producer NF,receiving the SBI message indicating the intent to use zero eventnotification messaging, and, transmitting a zero event notificationrequest message to the consumer NF using a callback uniform resourceidentifier (URI) from the SBI message to confirm the callback URI andconnectivity from the producer NF to the consumer NF. The steps furtherinclude, at the consumer NF, receiving the zero event notificationrequest message and, in response, sending a zero event notificationresponse message to the producer NF. The steps further include, at theproducer NF, receiving the zero event notification response message,and, in response, continuing SBI subscription messaging with theconsumer NF.

The subject matter described herein can be implemented in software incombination with hardware and/or firmware. For example, the subjectmatter described herein can be implemented in software executed by aprocessor. In one exemplary implementation, the subject matter describedherein can be implemented using a non-transitory computer readablemedium having stored thereon computer executable instructions that whenexecuted by the processor of a computer control the computer to performsteps. Exemplary computer readable media suitable for implementing thesubject matter described herein include non-transitory computer-readablemedia, such as disk memory devices, chip memory devices, programmablelogic devices, and application specific integrated circuits. Inaddition, a computer readable medium that implements the subject matterdescribed herein may be located on a single device or computing platformor may be distributed across multiple devices or computing platforms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a network diagram illustrating an exemplary 5G system networkarchitecture;

FIG. 2A is a message flow diagram illustrating exemplary messagesexchanged for creating a subscription on the SBI interface;

FIG. 2B is a message flow diagram illustrating exemplary messageexchanged for Sending a notification message relating to an existingsubscription;

FIG. 3 is a message flow diagram illustrating exemplary messagesexchanged for creating a subscription and transmitting a notificationmessage where the notification message is not successfully delivered tothe consumer NF;

FIG. 4 is a message flow diagram illustrating an exemplary process forzero event notification as part of a new subscription;

FIG. 5 is a message flow diagram illustrating exemplary messagesexchanged for zero event notification after a new subscription;

FIG. 6 is a message flow diagram illustrating exemplary messagesexchanged for zero event notification as part of a subscription update;

FIG. 7 is a message flow diagram illustrating exemplary messagesexchanged for zero event notification after a subscription update;

FIG. 8 is a block diagram illustrating an exemplary architecture for aconsumer NF and a producer NF for performing zero event notification;and

FIG. 9 is a flow chart illustrating an exemplary process for improvedSBI message transport using zero event notification.

DETAILED DESCRIPTION

FIG. 1 is a block diagram illustrating an exemplary 5G system networkarchitecture. The architecture in FIG. 1 includes NRF 100 and SCP 101,which may be located in the same home public land mobile network(HPLMN). As described above, NRF 100 may maintain profiles of availableproducer NF service instances and their supported services and allowconsumer NFs or SCPs to subscribe to and be notified of the registrationof new/updated producer NF service instances. SCP 101 may also supportservice discovery and selection of producer NF instances. SCP 101 mayperform load balancing of connections between consumer and producer NFs.

NRF 100 is a repository for NF or service profiles of producer NFinstances. In order to communicate with a producer NF instance, aconsumer NF or an SCP must obtain the NF or service profile of theproducer NF instance from NRF 100. The NF or service profile is aJavaScript object notation (JSON) data structure defined in 3GPP TS29.510. The NF or service profile definition includes at least one of afully qualified domain name (FQDN), an Internet protocol (IP) version 4(IPv4) address or an IP version 6 (IPv6) address.

In FIG. 1 , any of the network functions can be consumer NFs, producerNFs, or both, depending on whether they are requesting, providing, orrequesting and providing services. In the illustrated example, the NFsinclude a PCF 102 that performs policy related operations in a network,a UDM function 104 that manages user data, and an application function(AF) 106 that provides application services.

The NFs illustrated in FIG. 1 further include a session managementfunction (SMF) 108 that manages sessions between access and mobilitymanagement function (AMF) 110 and PCF 102. AMF 110 performs mobilitymanagement operations similar to those performed by a mobilitymanagement entity (MME) in 4G networks. An authentication serverfunction (AUSF) 112 performs authentication services for user equipment(UEs), such as user equipment (UE) 114, seeking access to the network.

A network slice selection function (NSSF) 116 provides network slicingservices for devices seeking to access specific network capabilities andcharacteristics associated with a network slice. A network exposurefunction (NEF) 118 provides application programming interfaces (APIs)for application functions seeking to obtain information about Internetof things (IoT) devices and other UEs attached to the network. NEF 118performs similar functions to the service capability exposure function(SCEF) in 4G networks.

A radio access network (RAN) 120 connects user equipment (UE) 114 to thenetwork via a wireless link. Radio access network 120 may be accessedusing a g-Node B (gNB) (not shown in FIG. 1 ) or other wireless accesspoint. A user plane function (UPF) 122 can support various proxyfunctionality for user plane services. One example of such proxyfunctionality is multipath transmission control protocol (MPTCP) proxyfunctionality. UPF 122 may also support performance measurementfunctionality, which may be used by UE 114 to obtain network performancemeasurements. Also illustrated in FIG. 1 is a data network (DN) 124through which UEs access data network services, such as Internetservices.

SEPP 126 filters incoming traffic from another PLMN and performstopology hiding for traffic exiting the home PLMN. SEPP 126 maycommunicate with an SEPP in a foreign PLMN which manages security forthe foreign PLMN. Thus, traffic between NFs in different PLMNs maytraverse two SEPP functions, one for the home PLMN and the other for theforeign PLMN.

As described above, one problem with the 3GPP network architecture for5G networks is that notifications from a producer NF to a consumer NFrelating to an existing a subscription may fail due to a number ofreasons, including an invalid callback URI in a subscription requestmessage, a transport failure between the consumer NF and the producerNF, firewall misconfigurations, etc. It is desirable to identify sucherrors rapidly so that notification messages can be delivered withincreased reliability. Identifying invalid callback URIs and lack ofconnectivity from a producer NF to a consumer NF should be performedusing a mechanism that is easy to implement at the NF service consumerand the NF service producer and that results in rapid erroridentification so that appropriate corrective action can be taken.

FIG. 2A is a message flow diagram illustrating an NF service consumercreating a subscription with an NF service producer over the SBIinterface using the HTTP POST method. Referring to FIG. 2A, in line 1,NF service consumer 200 sends a subscription request carried in an HTTPPOST message to NF service producer 202. The subscription requestmessage identifies a subscription being created and includes a callbackURI for sending notifications to NF service consumer 200. In response tothe subscription request message, in line 2, NF service producer 202creates the requested subscription and responds to the subscriptionrequest message with a subscription response message, which in theillustrated example is an HTTP 201 Created message, indicating that thesubscription has been created. It should be noted that once asubscription is created, there is no mechanism for verifying thecallback URI in the subscription request or connectivity from theproducer NF to the consumer NF prior to sending a notification messageto the consumer NF.

FIG. 2B illustrates the use of the HTTP POST method to send anotification regarding an existing subscription to a consumer NF.Referring to FIG. 2B, in line 1 of the message flow diagram, NF serviceproducer 202 sends an HTTP POST message to NF service consumer 200containing a notification triggered by a condition specified in anexisting subscription. The notification message is sent to the callbackURI in the subscription request message. In line 2, NF service consumer200 responds with a 200 OK or 204 No Content message, depending onwhether the POST operation was successful. If the callback URI in thesubscription request is invalid or there is a lack of connectivity fromthe NF service producer to the NF service consumer, the NF serviceconsumer will not receive the notification message in FIG. 2B, and thereis no feedback mechanism for increasing reliability of delivering thenotification message.

One problem with the subscription procedure illustrated in FIGS. 2A and2B is that the delivery of the notification message illustrated in FIG.2B can fail and there is no mechanism for reducing the likelihood offailure to successfully deliver the notification message prior totransmitting the notification message. As indicated above, notificationmessages can fail because of a bad callback URI, a transport failurearising because of a transport layer security misconfiguration, asecurity failure because of a firewall rule misconfiguration, or othermechanism. An out-of-band procedure is needed to make sure that an NFservice producer can notify the NF service consumer successfully. Theout-of-band procedure becomes complex when the same operator does notown both the NF service consumer or the NF service producer, forexample, in the case of a mobile network operator-mobile virtual networkoperator (MNO-MVNO) interaction and roaming scenarios. A feedbackmechanism is needed to tell both the service producer and the serviceconsumer about the inability of the service producer to send thenotification message. In one implementation described herein, thefeedback mechanism occurs prior to transmitting a notification messagetriggered by a condition associated with a subscription through theexchange of zero event notification request and response messages fromthe NF service producer to the NF service consumer.

FIG. 3 illustrates the problem that can occur when a notification fails.Referring to FIG. 3 , in line 1 of the message flow diagram, NF serviceconsumer 200 sends a subscription request message to NF service producer202. In line 2 of the message flow diagram, NF service producer 202sends a subscription response to NF service consumer 200 indicating thatthe subscription was successfully created. In line 3 of the message flowdiagram, when the notification condition associated with thesubscription is triggered, NF service producer 202 sends a notificationrequest message to NF service consumer 200. However, delivery of thenotification request fails, for example, due to any of the causesdescribed above. When this occurs, NF service consumer 200 is requiredto detect the failure and correct or attempt to correct the issue thatcaused the failure and possibly recreate the subscription. Detecting thefailure may be difficult, because NF service consumer 200 doesn't knowthat the notification message was transmitted. Stated differently, it isdifficult for a receiver (in this case the NF service consumer) todetect failed transmission of a notification message that the NF serviceconsumer did not receive.

In light of these difficulties, the subject matter described hereinincludes a procedure for zero event notification where NF serviceproducer 202 sends a zero event notification request message to NFservice consumer 200 to confirm the availability of NF service consumer200 to receive a notification message relating to a subscription, and NFservice consumer 200, in response to the zero event notification requestmessage, transmits a zero event notification response message to NFservice producer 202. As used herein, the term “zero event notificationrequest message” refers to a dummy notification request message that isnot triggered by a notification event and is used by the NF serviceproducer to verify that the callback URI in a subscription request isvalid and that connectivity with the consumer NF is available. The term“zero event notification response message” refers to a dummynotification response message that confirms receipt of the zero eventnotification request message.

FIG. 4 is a message flow diagram illustrating the use of the zero eventnotification message procedure as part of a new subscription to verify acallback URI and confirm connectivity with a consumer NF. Referring tothe message flow in FIG. 4 , in line 1, NF service consumer 200 sends asubscription request message to NF service producer 202. Thesubscription request message includes an identifier for thesubscription, a callback URI, and a parameter that indicates the intentto use zero event notification as part of the subscription creationprocedure. The parameter that indicates the usage of zero eventnotification as part of the subscription creation procedure may becarried as a new parameter in an HTTP header of the subscription requestmessage.

In line 2 of the message flow diagram, NF service producer 202 sends azero event notification request message using the callback URI from thesubscription request and sends the message to NF service consumer 200 toverify the callback URI and connectivity from NF service producer 202 tothe NF service consumer 202. If the zero event notification requestmessage is successfully received, control proceeds to line 3 a where NFservice consumer 200 sends a zero event notification response message toNF service producer 202 indicating successful receipt of the zero eventnotification request message. Control then proceeds to line 4 a where NFservice consumer 202 sends a subscription response message to NF serviceconsumer 200 indicating successful creation of the subscription. Thus,lines 1, 2 a, 3 a, and 4 a of FIG. 4 illustrate the use of the zeroevent notification procedure to confirm or verify the callback URI andconnectivity with NF service consumer 200 to receive notificationmessages where the zero event notification procedure is performed aspart of the subscription creation procedure.

Referring to step 2B in FIG. 4 , if NF service producer 202 is unable tosend the zero event notification request message, control proceeds toline 4 b, where NF service producer 202 sends a subscription responsemessage indicating failure to establish a subscription. Control thenproceeds to line 5 where NF service consumer 200 retries thesubscription request after correcting the cause of the previoussubscription failure. In line 6, NF service producer 202 sends a zeroevent notification request message to NF service consumer 200. In line7, NF service consumer 200 sends a zero event notification response toNF service producer 202. In line 8, NF service producer 202 sends asubscription response to NF service consumer 200 indicating successfulcreation of the subscription. Thus, FIG. 4 illustrates the use of thezero event notification procedure to verify the callback URI andconnectivity of the consumer NF to receive a subscription responsemessage and subsequent notifications as part of establishment of a newsubscription.

In an alternate implementation, the zero event notification proceduremay be used to confirm the callback URI and connectivity with the NFservice consumer to receive notification messages after creation of anew subscription. This scenario is illustrated in FIG. 5 . Referring toFIG. 5 , in line 1, NF service consumer 200 sends a subscription requestto NF service producer 202. The subscription request indicates orcarries a parameter indicating an intent to use zero event notificationafter subscription creation. In line 2 of the message flow diagram, NFservice producer 202 sends a subscription response message to NF serviceconsumer 200 confirming creation of the subscription. In step 3, NFservice consumer 200 waits for the dummy or zero event notificationrequest message to arrive and, based on an operator configuration,generates an alert if the zero event notification request message doesnot arrive within a configured time, as indicated by the dummynotification timeout in step 5 b. Assuming NF service producer 202 isable to send the zero event notification request message, controlproceeds to step 4 a, where NF service producer 202 sends the zero eventnotification request message to NF service consumer 200. If NF serviceconsumer 200 successfully receives and accepts the zero eventnotification request message, control proceeds to line 5 a where NFservice consumer 200 sends a zero event notification response message toNF service producer 202 indicating successful receipt of the zero eventnotification request message. After line 5 a, the zero eventnotification procedure ends, and subscription-related communications canthen proceed as normal between NF service consumer 200 and NF serviceproducer 202. For example, if an event occurs that triggers anotification, NF service producer 202 can send a notification messageregarding the event to NF service consumer 200. Because the zero eventnotification message exchange was successful, NF service producer 202may have a higher degree of confidence that the notification messagewill be successfully received than if the zero event notificationrequest and response message exchange had not successfully occurred.

Referring to step 4 b in FIG. 5 , if NF service producer 202 is unableto send the zero event notification request message, the dummynotification timeout in step 5 b occurs, and control proceeds to step 6where NF service consumer 200 and NF service producer 202 react based onthe operation result and operator configuration. For example, NF serviceconsumer 200 may delete the subscription, attempt to re-establish thesubscription, and reset the timer for waiting for the zero eventnotification request message after the new subscription is established.Thus, FIG. 5 illustrates the case of using the zero event notificationprocedure to confirm a callback URI and connectivity with an NF serviceconsumer to receive notification messages after establishment of asubscription.

In an alternate implementation of the subject matter described herein,the zero event notification procedure may be implemented as part of asubscription update. Such an implementation is illustrated in FIG. 6 .Referring to FIG. 6 , in line 1 of the message flow diagram, NF serviceconsumer 200 sends a subscription update request message to NF serviceproducer 202. The subscription update request message may be an HTTP PUTor PATCH message relating to an existing subscription. The subscriptionupdate request message may include a parameter in a header of themessage indicating the intent to use zero event notification as part ofthe subscription update procedure. In step 2 a, NF service producer 202sends a zero event notification request message to NF service consumer200 using the callback URI from the subscription update request toverify the callback URI and connectivity from the NF service producer tothe NF service consumer. If the subscription update request message inline 1 includes an updated callback URI, then NF service producer 202uses the updated callback URI in the zero event notification requestmessage. If NF service consumer 200 successfully receives the zero eventnotification request message, NF service consumer 200 responds in line 3a by sending a zero event notification response message to NF serviceproducer 202 indicating successful completion of the zero eventnotification procedure. After step 3 a, control proceeds to step 4 awhere NF service producer 202 sends a subscription update responsemessage to NF service consumer 200 indicating that the subscriptionupdate was successful. Thus, lines 1, 2 a, 3 a, and 4 a in FIG. 6illustrate the successful use of the zero event notification procedureas part of a subscription update to verify a callback URI presented in asubscription update request and to verify connectivity from an NFservice producer to an NF service consumer.

Referring to step 2B in FIG. 6 , if NF service producer 202 is unable tosend the zero event notification request, control proceeds to step 3 bwhere NF service consumer 200 sends a zero event notification responsefailure message to NF service producer 202. Control then proceeds tostep 4 b where NF service producer 202 sends a subscription updatefailure message to NF service consumer 200. Control then proceeds tostep 5 where NF service consumer 200 retries the subscription updaterequest after fixing the root cause for the previous subscription updatefailure. In step 6, NF service producer 202 sends a zero eventnotification request message to NF service consumer 200. In step 7, NFservice consumer 200 sends a zero event notification response messageindicating successful receipt of the zero event notification requestmessage. In response to receiving the zero event notification responsemessage, in line 8, NF service producer 202 sends a subscription updateresponse message to NF service consumer 200 indicating successfulupdating of the subscription.

Referring to line 3 b in FIG. 6 , if NF service consumer 200 receivesthe zero event notification request message and is unable to respond,control proceeds to step 4 b where NF service producer 202 sends asubscription update failure message to consumer NF 200. Consumer NF 200may then perform steps 5-8 of retrying the subscription update and thezero event notification procedures. Thus, FIG. 6 illustrates the use ofthe zero event notification procedure as part of a subscription updateprocess to verify a callback URI in a subscription update requestmessage and connectivity from the producer NF to the consumer NF.

In an alternate implementation of the subject matter described herein,the zero event notification procedure may be performed after asubscription update. This implementation is illustrated in FIG. 7 .Referring to FIG. 7 , in line 1, NF service consumer 200 sends asubscription update request to NF service producer 202. The subscriptionupdate request includes a parameter that indicates an intent to use thezero event notification procedure after the subscription updateprocedure is completed. In line 2 of the message flow diagram, NFservice producer 202 responds to the subscription update request. Instep 3, NF service consumer 200 waits for the zero event notificationrequest from NF service producer 202. In line 4 a, NF service producer202 sends the zero event notification request to NF service consumer 200using the callback URI in the subscription update request message. Ifthe zero event notification request message is received by consumer NF200 within the configured timeout period, control proceeds to step 5 awhere consumer NF 200 sends a zero event notification response messageto producer NF 202 indicating successful completion of the zero eventnotification procedure. After successful receipt of the zero eventnotification response message, producer NF 202 can continuecommunicating with consumer NF 200 using subscribe/notifycommunications. with a high degree of confidence that the notificationmessages will be received.

Returning to step 3 in FIG. 7 , if the zero event notification requestmessage does not arrive within the configured time period at NF serviceconsumer 200, for example, because the message is lost in transit, asindicated in step 4 b, because NF service producer 202 is unable to sendthe zero event notification request message, or because NF serviceproducer 202 sends the zero event notification request message to aninvalid callback URI, control proceeds to step 5 b where the dummy orzero event notification timeout occurs. In response to the dummy or zeroevent notification timeout, NF service consumer 200 sends a zero eventnotification response message indicating failure of the zero eventnotification procedure. Control then proceeds to step 6 where NF serviceconsumer 200 and NF service producer 202 react based on the operationresult and operator configuration. For example, NF service producer 202and NF service consumer 200 may attempt to repeat the zero eventnotification procedure and/or the subscription update procedure (e.g.,using a different callback URI).

FIG. 8 is a block diagram illustrating an exemplary architecture forconsumer NF 200 and producer NF 202 for implementing zero eventnotification as described herein. Referring to FIG. 8 , consumer NF 200and producer NF 202 each include at least one processor 800 and memory802. Consumer NF 200 includes a consumer side zero event notificationmanager 804 for performing consumer side zero event notificationprocessing. For example, consumer side zero event notification manager804 may generate the parameter that is included in a header of an HTTPsubscription request or subscription update request to indicate theintent to participate in the zero event notification procedure and whenthe procedure will be performed. Consumer side zero event notificationmanager 804 may also generate zero event notification response messagesfor the different scenarios illustrated in FIGS. 4-7 . Consumer sidezero event notification manager 804 may also keep the requisite timersfor waiting for zero event notification request messages from NF serviceproducer 202.

Producer NF 202 includes producer side zero event notification manager806. Producer side zero event notification manager 806 performs producerside zero event notification processing. Such processing or operationsinclude processing the header parameter received from NF serviceconsumer 200 indicating the intent to participate in the zero eventnotification procedure and implementing the zero event notificationprocedure at the requested time, e.g., as part of subscription creation,after subscription creation, as part of subscription updating, or aftersubscription updating. Producer side zero event notification manager 806may also generate zero event notification request messages and processzero event notification response messages to implement the scenariosillustrated in FIGS. 4-7 .

FIG. 9 is a flow chart illustrating an exemplary process for reliableSBI message transport using zero event notifications. Referring to FIG.9 , in step 900, the process includes, at a consumer NF, sending an SBImessage to a producer NF indicating an intent to use zero intent zeroevent notification messaging. For example, a NF service consumer, suchas NF service consumer 200 may send a subscription creation message or asubscription update message that includes an HTTP header with aparameter that indicates an intent to use zero event notificationmessaging. The header may also indicate the timing of using the zeroevent notification messaging. Example timings include using the zeroevent notification procedure as part of subscription creation, aftersubscription creation, as part of subscription updating, or aftersubscription updating.

In step 902, the process includes, at the producer NF, receiving the SBImessage indicating the intent to use zero event notification messagingand transmitting a zero event notification request message to theconsumer NF using the callback URI in the zero event notificationrequest message to verify the callback URI and connectivity from theproducer NF to the consumer NF. For example, an NF service producer,such as producer NF 202 may generate a zero event notification requestmessage and send the message to NF service consumer 200 at the timingspecified by the parameter in the SBI message.

In step 904, the process includes, at the NF service consumer, receivingthe zero event notification request message and, in, response, sending azero event notification response message to the producer NF. Forexample, consumer NF 200 may send a zero event notification responsemessage to producer NF 202 indicating successful receipt of the zeroevent notification request message

In step 906, the process includes, at the producer NF, receiving thezero event notification response message and, in response, continuingSBI subscription messaging with the consumer NF. For example, NF serviceproducer 202 may continue creation of a subscription if the zero eventnotification message exchange occurs as part of the subscriptioncreation process. If the zero event notification message exchange occursafter the subscription creation process, NF service producer 202 maystart or continue to send notifications to NF service consumer 200 whena triggering event associated with the subscription occurs. If the zeroevent notification message exchange is implemented during thesubscription update process, NF service producer 202 may continue thesubscription update messaging by sending a successful subscriptionupdate response message to NF service consumer 200. If the zero eventnotification message exchange is implemented after the subscriptionupdate process, NF service producer 202 may start or continue to sendnotifications to NF service consumer 200 using the updated subscriptioninformation.

Advantages of the subject matter described herein include increasedreliability of communications on the SBI interface for subscriptionrelated messaging. The zero event notification procedure may beapplicable to both intra- and inter-PLMN messages. The zero eventnotification procedure may be implemented between any pair of consumerand producer NFs to increase reliability of subscribe/notifycommunications. Examples of producer and consumer NFs that may implementthe subject matter described herein include the NRF, the PCF, thebinding support function (BSF), the NSSF, the user data repository(URD), the UDM, and the NEF.

The disclosure of each of the following references is herebyincorporated herein by reference in its entirety.

REFERENCES

-   1. 3GPP TS 23.501 V16.7.0 (2020-12) 3rd Generation Partnership    Project; Technical Specification Group Services and System Aspects;    System Architecture for the 5G System (5GS); Stage 2 (Release 16).-   2. 3GPP TS 23.502 V16.7.1 (2021-01), 3rd Generation Partnership    Project; Technical Specification Group Services and System Aspects;    Procedures for the 5G System (5GS); Stage 2 (Release 16).-   3. 3GPP TS 29.501 V17.0.0 (2020-12) 3rd Generation Partnership    Project; Technical Specification Group Core Network and Terminals;    5G System; Principles and Guidelines for Services Definition; Stage    3 (Release 17).

It will be understood that various details of the subject matterdescribed herein may be changed without departing from the scope of thesubject matter described herein. Furthermore, the foregoing descriptionis for the purpose of illustration only, and not for the purpose oflimitation, as the subject matter described herein is defined by theclaims as set forth hereinafter.

What is claimed is:
 1. A method for providing for reliable service basedinterface (SBI) message transport using zero event notifications, themethod comprising: at a consumer NF, sending an SBI message to aproducer NF indicating an intent to use zero event notificationmessaging, wherein zero event notification messaging comprises anexchange of a dummy notification request message that does notcorrespond to a notification event and a dummy notification responsemessage to verify a callback uniform resource identifier (URI) of theconsumer NF and that connectivity to the consumer NF is available; atthe producer NF, receiving the SBI message indicating the intent to usezero event notification messaging, and, transmitting a zero eventnotification request message to the consumer NF using a callback URIfrom the SBI message to confirm the callback URI and connectivity fromthe producer NF to the consumer NF, wherein the zero event notificationrequest message comprises a dummy notification request message that isnot triggered by a notification event and is used by the producer NF toverify that the callback URI in the SBI message is valid and thatconnectivity with the consumer NF is available; at the consumer NF,receiving the zero event notification request message and, in response,sending a zero event notification response message to the producer NF,wherein the zero event notification response message comprises a dummynotification response message to verify that the callback URI in the SBImessage is and that connectivity with the consumer NF is available; andat the producer NF, receiving the zero event notification responsemessage, determining that the callback URI in the SBI message is validand that connectivity with the consumer NF is available, and, inresponse, continuing SBI subscription messaging with the consumer NF. 2.The method of claim 1 wherein sending the SBI message indicating anintent to use zero event notification messaging includes transmitting ahypertext transfer protocol (HTTP) message to the producer NF andincluding a parameter in a header of the HTTP message that indicates theintent to use zero event notification messaging and a timing as to whento use the zero event notification messaging.
 3. The method of claim 2wherein the HTTP header indicates that the zero event notificationmessaging will be during or after subscription creation.
 4. The methodof claim 1 wherein transmitting the zero event notification requestmessage includes transmitting the zero event notification requestmessage as a part of creation of a subscription.
 5. The method of claim4 wherein transmitting the zero event notification request message aspart of creation of a subscription includes transmitting the zero eventnotification request message after receiving a subscription request fromthe consumer NF and wherein continuing the SBI subscription messagingwith the consumer NF includes transmitting a subscription response tothe consumer NF indicating successful creation of a subscription.
 6. Themethod of claim 1 wherein transmitting the zero event notificationrequest message includes transmitting the zero event notificationrequest message after creation of a subscription.
 7. The method of claim6 wherein transmitting the zero event notification request message aftercreation of a subscription includes transmitting the zero eventnotification request message after transmitting a subscription responsemessage to the consumer NF indicating successful creation of thesubscription.
 8. The method of claim 1 wherein transmitting the zeroevent notification request message includes transmitting the zero eventnotification request message as part of updating a subscription.
 9. Themethod of claim 1 wherein transmitting the zero event notificationrequest message includes transmitting the zero event notificationrequest message after updating a subscription.
 10. A system forproviding for reliable service based interface (SBI) message transportusing zero event notifications, the system comprising: a consumer NFincluding at least one processor and a memory for sending an SBI messageindicating an intent to use zero event notification messaging, whereinzero event notification messaging is an exchange of a dummy notificationrequest message that does not correspond to a notification event and adummy notification response message to verify a callback uniformresource identifier (URI) of the consumer NF and that connectivity tothe consumer NF is available; and a producer NF including at least oneprocessor and a memory for receiving the SBI message indicating theintent to use zero event notification messaging, and, in response, fortransmitting a zero event notification request message to the consumerNF using a callback uniform resource identifier URI from the SBI messageto confirm the callback URI and connectivity from the producer NF to theconsumer NF, wherein: the zero event notification request messagecomprises a dummy notification request message that is not triggered bya notification event and is used by the producer NF to verify that thecallback URI in the SBI message is valid and that connectivity with theconsumer NF is available; the consumer NF is configured to receive thezero event notification request message and, in response, send a zeroevent notification response message to the producer NF, wherein the zeroevent notification response message comprises a dummy notificationresponse message to verify that the callback URI in the SBI message isand that connectivity with the consumer NF is available to verify thatthe callback URI in the SBI message is and that connectivity with theconsumer NF is available; and the producer NF is configured to receivethe zero event notification response message, determining that thecallback URI in the SBI message is valid and that connectivity with theconsumer NF is available, and, in response, continue with SBIsubscription messaging with the consumer NF.
 11. The system of claim 10wherein the consumer NF is configured to send the SBI message indicatingan intent to use zero event notification messaging by transmitting ahypertext transfer protocol (HTTP) message to the producer NF andincluding a parameter in a header of the HTTP message that indicates theintent to use zero event notification messaging and a timing as to whento use the zero event notification messaging.
 12. The system of claim 11wherein the HTTP header indicates that the zero event notificationmessaging will be during or after subscription creation.
 13. The systemof claim 10 wherein the producer NF is configured to transmit the zeroevent notification request message as a part of creation of asubscription.
 14. The system of claim 13 wherein the producer NF isconfigured to transmit the zero event notification request message afterreceiving a subscription request from the consumer NF and to continuethe SBI subscription messaging with the consumer NF by transmitting asubscription response to the consumer NF indicating successful creationof a subscription.
 15. The system of claim 10 wherein the producer NF isconfigured to transmit the zero event notification request message aftertransmitting a subscription response message to the consumer NFindicating successful creation of the subscription.
 16. The system ofclaim 10 wherein the producer NF is configured to transmit the zeroevent notification request message as part of updating a subscription.17. The system of claim 10 wherein the producer NF is configured totransmit the zero event notification request message after updating asubscription.
 18. A non-transitory computer readable medium havingstored thereon executable instructions that when executed by a processorof a computer control the computer to perform steps comprising: at aconsumer network function (NF), sending a service based interface (SBI)message to a producer NF indicating an intent to use zero eventnotification messaging, wherein zero event notification messaging is anexchange of a dummy notification request message that does notcorrespond to a notification event and a dummy notification responsemessage to verify a callback uniform resource identifier (URI) of theconsumer NF and that connectivity to the consumer NF is available; atthe producer NF, receiving the SBI message indicating the intent to usezero event notification messaging, and, transmitting a zero eventnotification request message to the consumer NF using a callback URIfrom the SBI message to confirm the callback URI and connectivity fromthe producer NF to the consumer NF, wherein the zero event notificationrequest message comprises a dummy notification request message that isnot triggered by a notification event and is used by the producer NF toverify that the callback URI in the SBI message is valid and thatconnectivity with the consumer NF is available; at the consumer NF,receiving the zero event notification request message and, in response,sending a zero event notification response message to the producer NF,wherein the zero event notification response message comprises a dummynotification response message to verify that the callback URI in the SBImessage is and that connectivity with the consumer NF is available; andat the producer NF, receiving the zero event notification responsemessage, determining that the callback URI in the SBI message is validand that connectivity with the consumer NF is available, and, inresponse, continuing SBI subscription messaging with the consumer NF.